Currently, the process of growing phosphosilicate glass (PSG) by high-density plasma chemical vapor deposition (HDP CVD) (collectively referred to as HDP PSG) has been widely adopted in contact hole layer formation at 130 nm technology node and below. In order to meet requirements on gap-fill, it is a common practice to use helium (He) rather than argon (Ar) as a sputtering gas in HDP CVD processes at 130 nm technology node and below.
However, due to certain characteristics of an He-based HDP PSG process, it is prone to form a profile of a flower-shaped crust, referred to as a “flower pattern”, hung over each of the pattern areas, as shown in FIG. 2. Although some devices are fabricated by employing self-aligned processes for forming contact holes using PSG with a high phosphorus concentration (9%) to meet practical needs, different devices may have different requirements for the PSG processes. In most of the logic processes, the contact hole layer is generally formed by adopting a phosphorus concentration of 4% and it is required to have a minimized size of the flower patterns so as to ensure the stability of a resulting device and the repeatability of an etching